Travel servomotor

ABSTRACT

A servomotor for a power brake system which includes a pressure responsive wall in a chamber separated by a partition from the working chamber of the servomotor.

7/1961 Cripe T VACUUM SOL/RC E I United States Patent [111 [72] Inventors Stanley l. MacDuff; 3,013,536 12/1961 Cripc 92/48X Maxwell L. Cripe, 401 N. Bendix Drive, 3,076,441 2/1963 Ayers, .lr. 9 l/434X South Bend, 1nd. 46620 3,151,532 10/1964 Ayers, .lr. 91/434X [21] Appl. No. 769,789 3,357,317 12/1967 Hager 91/434X [22] Filed Oct. 23, 1968 3,411,414 11/1968 Brown et a1.. 91/434X Patented Feb. 2, 1971 3,415,577 12/1968 Walker 303/21F 3,422,622 1/ 1969 Arentoft et a1. 60/54.5P 3,449,019 6/1969 Walker 303/21F [54] g Primary ExaminerMartin P. Schwadron Assistant Examiner-Robert R. Bunevich [52] US. Cl 91/33, Anomeys Richal-d Geib and Flame Arens, Ham Hix and 60/546; 91/434; 303/21 Smith, [51] Int. Cl F15b 7/08, Fl5b13/04, F15b 13/14 Field of Search /54, 516P, E; 91/32, 33. 370, 371, 372, 373, 434. 444, 448; 92/48, 49; 303/21 [56] References Cited ABSTRACT: A servomotor for a power brake system which UNITED STATES PATENTS includes a pressure responsive wall in a chamber separated by 2,993,478 60/54.6PX a partition from the working chamber of the servomotor.

PMENTEB FEHZ' ml ATTORNEYS TRAVEL SERVOMO'IOR RELATED APPLICATIONS SUMMARY In recent years the vehicle industry has expressed a desire for a servomotor for vehicle brakes of the vacuum over air type which has sufficient power to eliminate the need for manual effort. More particularly, it has been a desire to provide a vacuum over air servomotor with a valve mechanism that has minimum travel required to provide any brake pressure desired. It is the principal object of this invention to meet this need.

Another object of this invention is to provide a power brake device which is so constructed that, upon failure of the power source, the vehicle operator can apply the brakes by application of force and motion to the pedal, but which, when operating normally with an operable power source does not permit any force applied by the operator to be applied to the braking system or to affect the pressure therein.

I A more particular explanation of the object of this invention is to have a valve means linked to the working walls of a servomotor that drive piston means in a pressure generating device to permit the walls to move relative to the valve means under normal, boost power available conditions.

DRAWING DESCRIPTION I Other objects and advantages of this invention will most certainly appear to those skilled in the art from the following description of the drawings in which:

FIG. I is a cross section of a servomotor for an antiskid brake system in accordance with the principles of this design in which the various other components to complete the system are integrated therewith; and

FIG. 2 is a partial cross section of the servomotor only of FIG. I showing in detail the components added to a conventional type servomotor to bring about the adaptation of same for an antiskid brake system.

DETAILED DESCRIPTION While this invention has particular application to an adaptive brake system where it is desired that a vehicle operator be precluded from interfering with the antiskid control means by application of excessiveforce to the brake pedal because of his natural instincts, it will be readily obvious that the servomotor described hereinafter in reference to such utilization has a much broader scope of utilization.

With regard to FIG. I there is shown a servomotor I having a motor housing 12 and a master cylinder I4 that are mounted in a vehicle to be operable by a brake pedal 16. The servomotor as thus constituted, provides braking pressures via conduits I8 and to a front wheel disc brake actuator 22 and a load sensing proportioning valve 24 connected by a conduit 26 to a wheel cylinder 28 for the rear drum brakes 30, respectively. A vehicle wheel speed sensing mechanism 32 is operatively connected via a friction drive ring 34 to the front brake disc 36 to provide a signal to a computer mechanism 38 which is energized by means of a switch 40 whenever the brake pedal 16 is pivoted by the operator to engage the contacts associated with plunger 42 of the switch 40. The brake proportioning valve 24 is rendered responsive to vehicle weight shifting in that it has a lever arm 44 connected by a spring 46 to a bracket 48 depending from the vehicle frame 50 to regulate the transmission of braking pressure from the secondary chamber 52 of master cylinder 14 to the wheel cylinder 28. Details of the computer system 38 and the load proportioning valve 24 can be readily observed within the prior art and further reference thereto is not deemed necessary in order to explain their function to those skilled in the art of this invention.

The vehicle battery 54 provides the source of energy for the computer system 38 and a pair of solenoid valves 56 and 58 connected by conduit 60 to the control pressure chambers 62 and 64 of the motor I2. and by conduit 66 to reference pressure chambers 68 and 70 also ofthe motor [2. With regard to the motor envisioned so far it is a vacuum air-type motor wherein vacuum forms the reference pressure in chambers 68 and 70 and atmosphere entering via an inlet 72 of the valve mechanism forms the control pressure for chambers 62 and 64. The chambers are separated by wall means 74 and 76 connected by rolling diaphragms 78 and 80 to the housing formed of ends 82 and 84 with intermediate sections 86 and 88 joined together by bolts such as bolt 90 with the beads of diaphragms 78 and 80 interposed to seal the connection. In addition the valve mechanism is carried by a wall 92 having a rolling diaphragm 93 whose peripheral bead also acts as a seal between the end shell 84 and intermediate section 88 when joined by a bolt 90. End shells 82 and 84 have ports 96, 98 and I00, I02 provided therethrough; whereas inten'nediate section 86 has a port 104 and intermediate section 88 has ports I06 and I08 provided therethrough.

As seen, the conduit 66 is communicated via a vacuum check valve to the inlet port 96 and the vacuum source, which the skilled in the art will readily understand as being the intake manifold for the engine of the associated vehicle (not shown). A conduit 112 communicates port I00 to the sole noid valve 56, which will be explained in further detail hereinafter; whereas conduit 60 communicates ports I04 and I06 with the solenoid valves 56 and 58. Another conduit H4 is provided to be joined with the inlet port 98 and the inlet port 102 in the end shells 82 and 84, respectively, to communicate the reference pressure chamber 68 to a chamber II6 behind the valve carrying wall 92. The port I08 is opened to surrounding atmosphere to communicate chamber I18 ahead of the wall 92 to atmosphere at all times whereby vacuum being in chamber 116 and atmosphere being in chamber II8 will maintain the valve carrying wall 92 in the rear attitude shown in FIG. 1 and permit only limited travel of the valve operating mechanism.

Within the movable wall structure 92 the valve mechanism is arranged to comprise a followup type valve poppet I20 within a rearwardly projecting boss 122 that extends to the right, as viewed in the drawing, through the end 84. A movable valve seat member 124 is supported by the structure of the movable wall 92 and connected to a push rod I26 from the brake pedal 16 to be normally movable (or shiftable) to the left, as viewed in the drawing whereby the rubber poppet I20 will seat on annular valve seat 128 of the movable wall structure 92 so that further movement of the seat 124 will open the atmospheric inlet 72 to a discharge port I30 of the structure 92. In the condition of these valve elements shown, a reference pressure inlet port 132 is open around seat I28 to the discharge port I30. A conduit means I34 communicates the area within the boss I22 behind the seat 128 to a passageway I36 in the structure 92. This passageway I36 opens to a reaction pre'ssure chamber 138 in the structure 92 that is created therein by a diaphragm assembly I40 to also provide a reference pressure chamber I42 on the other side of the diaphragm assembly 140. A counterreaction spring I44 is located in the chamber 142 between the structure of the movable wall assembly 92 and the diaphragm asembly 140 to normally urge the latter to a forwardmost position whereby the volume of chamber I38 is at a minimum and the volume of chamber 142 is at a maximum. Chamber I42 is open by means of port 146 to the reference pressure chamber I16 behind the valve carrying wall structure 92. It should be noted that the conduit means 134 may be replaced by passage means completely internally of the structure 92.

Discharge port I30 for the valve carrying wall assembly 92 is connected by a conduit 148 to a fitting I50 within which an end portion I52 of conduit I12 is press fitted. End fitting I50 is sealingly retained in port 100 by means of a snap ring 154. Thus, the valve discharge port 130 is communicated to solenoid valve 56 for communication via conduits 60 to control pressure chambers 62 and 64. A return spring 156 is assembled between end shell 82 and the wall 74 to maintain the normal released position of the walls 74 and 76 connected together by means of a hub 158 having bores 160 and 162 from opposite ends receiving a force transmitting rod 164 and push rod 166, respectively. The hub 158 is supported and sealed with respect to partitions depending from the intermediate structures 86 and 88 at spaced points and retained on the movable walls by snap ring provisions. Bore 160 also serves as a communication of reference pressure chamber 68 with reference pressure chamber 70 by means of radial ports 168 in front of and adjacent the connection of wall 76 with the hub 158.

Force transmitting rod 164 extends through the forward end of shell 82 to be connected with a primary piston 170 within a bore 172 of master cylinder 14. Primary piston 170 is in turn connected via a cage spring assembly 174 to a floating piston 176 whereby a primary chamber 178 is created between the pistons 170 and 176 and the secondary chamber 52 is between the piston 176 and the end of the bore 172. A return spring 180 is slightly compressed in the normal released attitude of pistons 170 and 176 between the piston 176 and the housing about the end of the bore 172 to maintain the released position of the pistons 170 and 176 and in addition provide a slight supplemental force for the return spring 156 of the motor 12. Thus the matter cylinder 14 is of a split-system-type capable of developing separate pressures, as aforementioned, from a supply of hydraulic fluid contained in separate reservoirs 182 and 184 closed by a common cap 186 and diaphragm 188 upon the assembly of bail 190 to housing 192 of master cylinder 14 to fit over cap 186 and normally reside in centrally located indentations (not shown).

With respect to FIG. 2, the conduits 114, 66 and 60 are shown in reversed attitude from that of FIG. 1; but, otherwise, there is no change in the structure of the motor 12 that is separately depicted in FIG. 2. Essentially the purpose of FIG. 2 is to show the integration of the solenoid valve 56 and 58 and their elements. More particularly, the solenoid valve 56 has a normally open valve poppet 192 carried by a resilient metal support 194 between the joint of valve housing 196 with a flanged opening 198 of conduit 60 to also act as a seal between this juncture. The support 194 may be in the form of spring fingers or a perforated diaphragm. Within the housing 196 a coil 200 and a core 202 are arranged behind a valve seat 204 facing the poppet 192. As indicated when using a metal diaphragm 194, a plurality of radial holes in the area between the poppet 193 and the peripheral sealing portion are provided in order to communicate around the periphery of poppet 192. In the position shown by FIG. 2 the chamber 206 communicable with conduit 112 is thus open to the interior of conduit 60 having connections 208 and 210 with ports 106 and 104, respectively.

Solenoid valve 58 also has a poppet 212 connected by a spring or resilient diaphragm 214 to the juncture of solenoid housing 216 with conduit 66 formed as a portion of conduit 60 in this design of FIG. 2. Again the solenoid housing has within it a coil 218 and a core 220 behind a valve seat 222 facing the poppet 212.

Spring or resilient diaphragms 194 and 214 of solenoid valves 56 and 58 are designed to maintain poppet 192 normally open and poppet 212 normally closed; i.e., poppet 212 seats on an opening 224 of conduit 66 into chamber 226 of valve 58 leading, via spaced radial passages in resilient diaphragm 214 to an opening 228 from chamber 226 to the interior of conduit 60. Both the poppets 192 and 212 have center areas 230 and 232, respectively, of a material which is attractable by cores 202 and 220, respectively.

In closing this description of a manner of construction of the structure meeting the concepts of our invention, the vacuum check valve 110 is shown to comprise a rubber poppet 234 snap fitted to housing core 236 to prevent entry of anything but vacuum to the reference pressure chamber 68 and the interior of conduit 66.

OPERATION With regard to the operation of the structure of our invention. it should be understood that when the vehicle operator depresses the brake pedal 16 and closes the contacts as sociated with plunger 42 of switch 40, he not only sets in motion the valve poppet and the movable valve seat 124, but activates the computer system 38 electrically connected to vehicle deceleration sensing means 32 on the front wheel brake disc 36. In that the poppet 193, see FIG. 2, is normally open, the vehicle operator will first lap the communication of reference pressure via inlet port 132 in valve structure 92 to the conduit 148 connected to valve discharge port and via conduit 112 andconduit 60 to the control chambers 62 and 64. Next he will open the atmospheric inlet 72 of the boss 122 of the valve carrying wall assembly 92 to provide a pressure differential via the same conduits to the chambers 62 and 64. This will then cause a projection of the force transmitting rod 164, a closure of compensating port means in the master cylinder housing 192 between the reservoirs 182 and 184 and the secondary and primary chambers 52 and 178, respectively. As there always exists atmospheric pressure in chamber 118 and vacuum is normally present in chamber 116, the brake pedal wall be permitted only limited movement; i.e., movement sufficient to fully open the movable seat 124 from the following type poppet 120. However, as the atmospheric pressure being introduced to control chambers 62 and 64 is also connected via conduit 134 and passage 136 to the left side of diaphragm assembly 140, it will provide a pressure for the reaction chamber 138 that will eventually overcome counterreaction spring 144 providing a reaction force on brake pedal 16 giving the operator a sense of feel of braking that will match his sense of deceleration in the operators compartment of the vehicle.

Whenever the braking pressure developed in the primary chamber 174 begins to approach a value that will lock the brake disc 36, the sensor 32 will call upon the computer system 38 to provide a signal first to the solenoid valve 56 to magnetize the core 202 and pull poppet 193 onto seat 204. This terminates the communication of the operator-operated control valve means comprising the movable seat 124 and followup poppet 120 from the control of pressure differential across walls 74 and 76. 1f the sensor 32 senses a further increase in deceleration of brake disc 36, the computer system 38 will then energize coil 218 to magnetize core 220 and thus pull poppet 212 away from opening 224 of conduit 66 to chamber 226. At this time vacuum will be drawnin conduit 60 between the now closed poppet 192 and the inner confines of control pressure chambers 62 and 64 whereby return springs 156 and any supplement due to hydraulic force in chambers 178 and 52 as well as the force of return spring 180 will cause a retraction of walls 74 and 76; but, more importantly. a retraction of pistons and 176 in the bore 172 will increase the displacement in the brake system whereby the vehicle braking action may be decreased until the sensor 32 signals the computer system 38 to again close the poppet 212 by release of the magnetism on core 220 sufficient to permit resilient diaphragm 214 to bring about this seating.

It should be noted that at the same time that this is going on, the vehicle weight is being shifted from the rear axle to the front axle and spring 46 is causing the closing of internal valving details of proportioning valve 24 to terminate the communication of conduit 20 with conduit 26. It should be understood by all that the pressure being supplied via conduit 26, valve 24 also is reactive in the valve to bring about continued modulation of the pressure to wheel cylinders 28 in accordance with the force of spring 46 on lever 44 regulating the biasing force on the elements within the valve 24 in opposition to the hydraulic pressure being delivered thereto via conduit 20 from the master cylinder 14.

Thus, whereas the front wheels are prevented from locking in view of a means sensing their rate of deceleration, the rear wheels are not only controlled off the front wheels, but in accordance with the load shifting caused by deceleration of the vehicle.

In the event of a control pressure loss such as the development of atmosphere within the vehicles engine intake manifold and the elimination of vacuum in reference pressure chambers 68, 70, and H6, the movable wall structure 92 is able to followup the movement of wall 74 or 76 and cause further movement thereof or, if this happens, initially the initial movement thereof to pressurize the primary and secondary chambers 178 and 52, respectively, of the master cylinder I4 to effect vehicle braking. Under these conditions, the antiskid system is still operative, however, the valves 56 and 58 would not be effective to permit the introduction of vacuum to the control chambers 62 and 64 so that they would not interfere in the manual braking by the vehicle operator.

Under no power available operation the push rod 166 moves hub I58 carrying wall 76 along and leaving wall 74, that is biased by return spring 156. behind. Therefore, under manual application of master cylinder 14 the spring 156 does not have to be overcome, and the master cylinder return spring 180 returns the structure on release of foot pressure on pedal 16.

It is therefore obvious that under powered operation hub I58 moves relative to push rod 166 and consequently to the wall 92 that is being held by atmospheric pressure from moving, as aforementioned.

Having fully described an operative construction of structure meeting the principles of my invention, it is now desired to set forth the intended protection sought by these Letters Patent in the appended claims.

We claim: l. A fluid pressure servomotor comprising: a housing having first and second pressure chambers; movable wall means in said pressure chambers for movement in response to a pressure differential across said movable wall means;

valve means in the first of said pressure chambers for controlling flow of fluid between said first pressure chamber and a pressure communicating port of the second of said pressure chambers, said valve means being actuated by a first force;

first control means for interrupting fluid flow between said first chamber and said pressure communicating port upon receiving a a source of vacuum pressure connected to a vacuum communicating port in said second chamber;

second control means for establishing communication between said pressure communicating port and said source of vacuum upon receiving a second signal, said communication being terminated before reestablishing fluid flow between said pressure communicating port and said first chamber;

force transmitting means operatively connected to said movable wall means in said second pressure chamber for exerting a second force which is greater than said first force in response to said pressure difference across said movable wall means and between said pressure communicating port and vacuum communicating port of said second chamber, said pressure difference moving said movable wall means in a given direction; and

resilient means for returning said movable wall to its original position after said pressure difference has been removed.

2. The fluid pressure servomotor, as recited in claim I. wherein said first and second control means alternately remove and reapply pressure across said movable wall means in said second pressure chamber in response to said first and second signals, respectively.

3. The fluid pressure servomotor, as recited in claim 2, further comprises: movable wall means in said first chamber for providing feel to an operator of said servomotor, upon loss of vacuum pressure said movable wall means operatmg with said force transmitting means to convey substantially all of said small force through said servomotor.

4. The fluid pressure servomotor, as recited in claim 3, further comprises a third pressure chamber with a movable wall therein, said third pressure chamber being connected with said second chamber about said force transmitting means to provide a further increase in said second force over said first force.

5. The fluid pressure servomotor, as recited in claim 2, wherein said first and second control means are solenoid operated valves. 7

6. The fluid pressure servomotor, as recited in claim 5, further comprising:

a diaphragmed cavity within the movable wall means in said first pressure chamber for giving feel to an operator of said braking system; and

vacuum communicating means for maintaining pressure balance in all chambers during nonoperation of said braking system.

33 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,559,532 Dated February 2, 1971 Inventor) STANLEY I. MacDUFF AND MAXWELL L. CRIPE It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Title, Delete "TRAVEL SERVOI'DTOR" insert ---NO TRAVEL SERVOI'DTOR--- Column 2, Line 19, Delete "93" and insert "-94-" Column 5, Line 48, After "a" insert ---first signal;-

Column 6, Line 44, Delete "braking system" and insert ---servomotor---. Line 47, Delete "braking system" and insert ---servomotor--- Signed and sealed this 1st day of May 1973.

(SEAL) Attest:

EDWARD M .FLE'I'CHER,JR ROBERT GOTTSCHALK Attesting Officer Commissionerof Pete: 

1. A fluid pressure servomotor comprising: a housing having first and second pressure chambers; movable wall means in said pressure chambers for movement in response to a pressure differential across said movable wall means; valve means in the first of said pressure chambers for controlling flow of fluid between said first pressure chamber and a pressure communicating port of the second of said pressure chambers, said valve means being actuated by a first force; first control means for interrupting fluid flow between said first chamber and said pressure communicating port upon receiving a a source of vacuum pressure connected to a vacuum communicating port in said second chamber; second control means for establishing communication between said pressure communicating port and said source of vacuum upon receiving a secOnd signal, said communication being terminated before reestablishing fluid flow between said pressure communicating port and said first chamber; force transmitting means operatively connected to said movable wall means in said second pressure chamber for exerting a second force which is greater than said first force in response to said pressure difference across said movable wall means and between said pressure communicating port and vacuum communicating port of said second chamber, said pressure difference moving said movable wall means in a given direction; and resilient means for returning said movable wall to its original position after said pressure difference has been removed.
 2. The fluid pressure servomotor, as recited in claim 1, wherein said first and second control means alternately remove and reapply pressure across said movable wall means in said second pressure chamber in response to said first and second signals, respectively.
 3. The fluid pressure servomotor, as recited in claim 2, further comprises: movable wall means in said first chamber for providing feel to an operator of said servomotor, upon loss of vacuum pressure said movable wall means operating with said force transmitting means to convey substantially all of said small force through said servomotor.
 4. The fluid pressure servomotor, as recited in claim 3, further comprises a third pressure chamber with a movable wall therein, said third pressure chamber being connected with said second chamber about said force transmitting means to provide a further increase in said second force over said first force.
 5. The fluid pressure servomotor, as recited in claim 2, wherein said first and second control means are solenoid operated valves.
 6. The fluid pressure servomotor, as recited in claim 5, further comprising: a diaphragmed cavity within the movable wall means in said first pressure chamber for giving feel to an operator of said braking system; and vacuum communicating means for maintaining pressure balance in all chambers during nonoperation of said braking system. 